Control Methods and Technical Key Points for Sunflower Brown Spot
Brown spot is one of the diseases that commonly occur in sunflowers, one of the main diseases causing yield loss and shriveled seeds in sunflowers, and one of the main reasons affecting their yield. So how should sunflowers be protected against brown spot? Let's take a look together.
1. Symptoms
When seedlings are affected, nearly circular lesions form on the cotyledons or young leaves; the front of the lesion is brown with a yellow halo around it, and the back is grayish-white. When plants are affected at the mature stage, irregular or polygonal brown lesions form on the leaves, surrounded by a yellow halo, with the center of the lesion gray and scattered with small black dots, which are the pathogen's conidia. In severe cases, the lesions merge into patches and the leaves wither and die; the petioles and stems can also be infected, developing narrow brown streaks. Its symptoms are somewhat similar to leaf spot, but the lesions of brown spot are larger and have concentric rings; when the weather is humid, brown mold-like growth appears on the lesions.
2. Occurrence Pattern
Brown spot overwinters as pycnidia or mycelium on diseased plant residues. When temperatures are suitable in spring and summer, especially during continuous rainy days, the pathogen multiplies in large numbers and releases abundant conidia, which spread by wind and rain. Generally, the disease is more severe in continuous-cropping fields and low-lying fields, in plots that had severe disease the previous year, and when field humidity is relatively high.
3. Agricultural Control
Crop rotation is the best way to prevent this disease. Rotating with gramineous crops for more than 3 years can greatly reduce the possibility of this disease occurring. Before planting, thoroughly remove diseased and dead leaves and deep-plow the soil to reduce the source of inoculum. At the same time, select varieties with strong disease resistance according to local conditions, plant at a reasonable density, apply sufficient well-rotted organic fertilizer, and strengthen the plants' disease resistance. Strengthen field management, drain water promptly after rain to reduce field humidity, and irrigate reasonably; flood irrigation should not be used.
4. Chemical Control
When the disease occurs, diseased leaves can be promptly removed while fungicides are sprayed for control. Brown spot is a fungal disease, and many fungicides have good effects on it, such as carbendazim, thiophanate-methyl, basic copper sulfate, basic copper sulfate, and other agents. Generally, spray once every 10 days, and 1-2 consecutive treatments are sufficient.
The above is an introduction to the control methods for sunflower brown spot. We hope it helps you. To learn more related knowledge, please stay tuned to us.